During a conversation with the French President, Johnson said it was "ridiculous" that the United Kingdom and France were only connected by the Channel Tunnel and suggested that a bridge could span the strait, the BBC reports. "Great meetings with French counterparts today". At it's narrowest point, the Channel is just over 20 miles wide.
But France's finance minister didn't foresee anyone bridging the Channel just yet. He said: "All ideas merit consideration, even the most far-fetched ones. Let's finish things already under way before thinking of new ones".
The world's longest bridge is China's Danyang-Kunshan Grand Bridge, a 102.4 mile long stretch of the Beijing-Shanghai high-speed railway.
But some experts have questioned the viability of a bridge crossing what is the busiest shipping channel in the world.
Sources close to Mr Johnson claimed the French president was enthusiastic about the idea of a new link.
A spokesperson for Prime Minister Theresa May was reported later to have said that there were no such plans.
Others pointed out that, technically, it's possible.
"You'd nearly certainly have to have vessel impact protection around the supports of the bridge so if anything hits it, it doesn't bring the bridge down".
Nigel Farage, the former leader of the nationalist U.K. Independence party, slammed the idea as unsafe and a waste of money.
He added: 'What was agreed yesterday, and I think that's what the foreign secretary tweeted about as well, is a panel of experts who will look at major projects together including infrastructure'. But what I would say is.we are going to have very good economic ties with France economically, culturally, in areas such as defence and security for many, many decades to come. Perhaps it was meant as a distraction from Thursday's summit where Macron rejected special post-Brexit access for Britain's financial services unless Britain played by the existing European Union rules.
Why is Boris Johnson quite so keen on improbable-sounding bridges?